Apple Senior VP of iPhone Software Scott Forstall demonstrates an app called Passbook at during the keynote at the Worldwide Developers Conference 2012 at Moscone West on Monday, June 11, 2012 in San Francisco, Calif.

As the Worldwide Developer Conference wrapped up in San Francisco last week, one application stood out for its potential to change the way we use our phones.

Passbook, an app that will be released along with the next version of Apple's mobile operating system, gathers loyalty cards, boarding passes, event tickets and coupons into a single virtual home. Apple presented it as a way to make shopping, traveling and seeing movies more efficient.

To some, Passbook represents a potential shift in the way we pay for goods. It's easy to imagine Apple allowing users to store payment-card information inside Passbook, marking the company's entry into a market that has grown crowded even as it has yet to crack the mainstream.

If the voice-powered assistant Siri was the star of last year's Apple releases, Passbook could be the app that steals the show this year. Much of the online commentary surrounding the company's WWDC announcements has focused on Apple's long-term plans for Passbook.

The big reason: Apple already has 400 million active credit cards on file in its iTunes store. At the moment, those cards are used primarily to buy digital music, movies and books. But one day those same accounts could let consumers buy physical goods.

"Clearly, this is the first step in Apple providing a digital wallet," said Charles Golvin, an analyst with Forrester Research.

The idea of a digital wallet has been more popular in theory than in practice. Like Internet-connected televisions and Android-powered tablets, the devices have been hyped by manufacturers but ignored by most consumers.

The same could once have been said about digital music, or tablet-style computers - other markets where early entrants gained little traction, only to see Apple find success by making simple what had once been complicated.

Demonstrating Passbook on stage, Apple executive Scott Forstall showed tickets, passes and coupons stacked neatly in a single app. Passbook is aware of the phone's location, he said, so when a user who buys a ticket online approaches a movie theater, a notification pops up with a link to the ticket ready to be scanned by an attendant.

Similarly, users who frequent a particular Starbucks could see their loyalty cards pop up on screen as soon as they approach the coffee shop.

Developers at WWDC attended sessions on how to create other items that can be stored in Passbook, which will expand the service's reach.

"With Passbook, we can anticipate Apple is positioned to really take mobile payments to a new level," said Krishna Subramanian, chief marketing officer of Velti, a mobile marketing firm. "Our data shows consumers are already growing in their willingness to shop and spend on mobile. ... It removes some of the previous barriers to spending on our phones."

Slow to catch on

To date, analysts say, a relatively small number of consumers pay for goods directly from their smart phones. Most companies have relied on near-field communications technology, or NFC, which uses a chip inside smart phones to communicate with dedicated merchant hardware. Apple products so far lack NFC technology.

Google announced its own digital wallet, called Google Wallet, a year ago. The limitations surrounding the product, which lets users tap their phones to pay for goods and services, are instructive. Wallet works only on a handful of phones, and has yet to become available on Verizon. It can connect to a single payments card - the Citi MasterCard, although users can also buy a prepaid card from Google. And Wallet can be used only where MasterCard's PayPass system is used; the company says there are about 140,000 such locations in the United States.

That's a lot for the average consumer to keep track of - particularly given that tapping a phone on a terminal may not seem like an improvement over swiping a payment card. Carriers like AT&T and Verizon, financial services companies like Visa and American Express, and startups like Square are building digital-wallet systems of their own. If and when Apple decides to enable payments on the iPhone, it will have plenty of competitors.

Valuable data

But even if credit cards never make it into Passbook, the app could still give Apple plenty of valuable data: where consumers shop, how often they frequent a given establishment, and what kind of offers move them to make purchases. With that data comes a range of new business opportunities for the company.

"Commerce is not just about payments," Golvin said. "Commerce is a chain, from the very beginning of thinking about something you might want to buy to choosing a particular brand, to deciding where to purchase it, to getting after care. It's a rich chain. And Apple's in a position to contribute to or influence it."